Translator Disclaimer
6 December 2002 Debunking the recurring myth of a magic wavelength for free-space optics
Author Affiliations +
Proceedings Volume 4873, Optical Wireless Communications V; (2002)
Event: ITCom 2002: The Convergence of Information Technologies and Communications, 2002, Boston, MA, United States
Free-Space Optics (FSO) is a proven, reliable technology for last mile telecommunications applications, used worldwide for both enterprise network building-to-building connections and for wireless access to more traditional land line communications networks. In most mid-latitude coastal cities, link availability at distances above a few hundred meters is primarily affected by fog and low clouds. At longer distances, heavy rain and snow can also affect the link. The most mature technology used in FSO equipment relies on low cost semiconductor lasers or LED’s operating in the near infrared at wavelengths of 785 nm or 850 nm. In the past few years, systems operating at 1550 nm have also been developed. At first the vendors of these systems claimed that the 1550 nm wavelength had better propagation characteristics in severe weather than the 785 nm wavelength. With further analysis and research, those claims were withdrawn. Now there are claims that even longer wavelengths near 10 microns will solve the FSO link availability issues associated with severe weather. Hype about such magic wavelengths for FSO is both a disservice to the investors who will lose the money they are investing based on exaggerated claims, and to the rest of the FSO industry which should be creating realistic expectations for the capability of its equipment. In the weather conditions which normally cause the highest attenuation for FSO systems, namely coastal fog and low clouds, 10 microns offers no propagation advantage over shorter wavelengths.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Eric J. Korevaar, Isaac I. Kim, and Bruce McArthur "Debunking the recurring myth of a magic wavelength for free-space optics", Proc. SPIE 4873, Optical Wireless Communications V, (6 December 2002);


Infrared radiative characteristics of water clouds
Proceedings of SPIE (September 15 1993)
Availability of airborne hybrid FSO/RF links
Proceedings of SPIE (June 02 2005)
Optical attenuation in fog and clouds
Proceedings of SPIE (November 27 2001)

Back to Top